Recently, the dimensions and weight of the housings of portable electronic apparatuses typified by cellular phones, smart phones, PDAs (Personal Digital Assistants), tablet-type terminals, and navigation terminals have been required to be reduced, from the viewpoint of compactness and lightweightness. Accordingly, demands have arisen for more compact antenna devices. It has also been required to allow a single portable terminal apparatus to communicate with a plurality of radio systems using different frequency bands.
Conventionally, therefore, as disclosed in, for example, patent literature 1, there has been proposed a multifrequency antenna device in which the second antenna element formed from a monopole element is provided at a position close to the feeding point of the first antenna element formed from a folded element with a stub in a direction opposite to the first antenna element.
However, it is difficult to expand the impedance band of the first antenna element of the conventional multifrequency antenna device itself. In order to expand the band, it is necessary to add the third antenna element to couple the first antenna element to the second antenna element. This inevitably increases the size of the antenna device.